Interleukine-3 (IL-3) is a T-cell derived lymphokine that promotes proliferation and differentiation of hematopoietic cells including the primitive erythroid precursors. Hemin, (a heme moiety) also augments the frequency of these cells in vitro. The specific aim of this project will be to develop an erythropoietin (EPO) independent system using these growth factors in combination. Also, to determine whether the combined effect would influence the growth kinetics of the Burst Forming Units (BFUe) of the chick yolk sac primitive erythroid cell population. Additionally, attempts will be made to grow the colonies in serum free-media. The long term objectives will be to compare the responsiveness to IL-3 and hemin between the primitive erythroid cell population of the yolk sac and the definitive cells of the embryo. To do this yolk sac membrane obtained from 3-5 days old embryos will be trypsinized and the cells harvested. After washings, cells will be incubated at 37C for up to 11 days in methycellulose cultures to obtain BFUe pure and mixed colonies. Erythroid colony hemoglobinization will be confirmed by staining with non carcinogenic benzidine and hematoxylin. Monoclonal antibodies will be included in culture to rule out the presence of endogenous EPO. Colonies will be scored and data evaluated by statistical analysis. Under conditions of irradiation, chemotherapy and bone marrow transplantation in normal and tumor bearing states, the employment of growth factors such as IL-3 and hemin will be important when used alone and in combination biotherapy. Also, in AIDS where T-cell population is depleted, the possible supply of growth factors in vivo may be instrumental in inducing the proliferation of other stem cell populations. Yolk sac is an easily accessible source of progenitor cells which have provided relevant information in the past regarding hemoglobin production. It is therefore potentially a useful source for providing understanding the malignant states. Students will benefit from this study because it incorporates the embryological with the hematological system. The goals are simple and attainable and is within the scope of our facilities here at Medgar Evers College.